I'm planning a Superior Hiking Trail thru + trails into the BWCA trip during late April / early May. Night temperatures should be mid to low thirties (assuming weatherspark.com is legit) and I'm trying to figure out a sleeping system.

I have the Arc'teryx Atom hooded jacket and the Atom pants that I've used comfortably with my 15 degree marmot down bag to about 10 degrees. At this point I'm pretty set on buying an Enlightened Equipment ProdigyX quilt, but I'm stuck on deciding which one, 50 or 40.

If I go with the 50 I save 6oz, but will that plus my warm midlayer be enough to keep me warm into the low thirties? Any advice is appreciated.

The difference between 32* weather and 39* weather is dramatic. If you were only expecting the latter, i'd say use the 50, but since the former is a possibility, use the 40. Of course, there are a few variables. If you sleep outside a lot the month before the trip, you can adjust your tolerance and get away with less. Your sleeping pad and shelter are also relevant.

If possible, test! I'm becoming a masochist when it comes to cold temperatures, and I always try to see what my lowest tolerance is for warmth. Over the course o the winter, my body adjusted dramatically.

If you added 6 oz with the 40, you'd be able to shed many more ounces by not bringing full fleece sleepwear, especially fleece pants (useless during the day). Use a super light down jacket and some synthetic tights like Under Armour.

I was trying to decide the same thing a couple of weeks ago and I decided to go with the 40* quilt. I noticed that the 40* quilt used 4.0 oz Apex Climasheld, and the same quilt last year was considered a 35* quilt. I figured the 40* would be the most versitle. Add a bivy and some extra clothes and should be okay down to freezing and if its really warm, it can be opened up flat and used as a blanket. I know you can save 6 oz with the 50* quilt, but when you are laying there shivering on a really cold night, 6 oz might not be a really big geal.

I agree with the others, go for the 40F as temps that time of year are unpredictable and better to have a little more versatility. You could save the wight by going with the RevX, it's a fantastic quilt.